1. Field of the Invention
The technology disclosed in the present specification relates to a semiconductor device and a method of manufacturing the same.
2. Description of Related Art
Japanese Patent Application Publication No. 2000-188399 (JP 2000-188399 A) has disclosed a semiconductor device using SiC and a method of manufacturing the same. In this semiconductor device, a p−type base region, an n−type source region and a source electrode are formed on a semiconductor substrate thereof. The n−type source region is formed on the surface of the p−type base region. The top surface of the n−type source region is in contact with the source electrode. In a deep layer of the n−type source region (a region on the p−type base region side), nitrogen having a relatively light mass has been doped as an n−type impurity. On the other hand, in the surface layer of the n−type source region (a region opposite to the p−type base region), phosphorus having a relatively heavy mass has been doped as an n−type impurity. According to the JP 2000-188399 A, when performing a heat treatment to activate impurities, the diffusion velocity of phosphorus decreases due to the larger mass than nitrogen thereby making external diffusion more difficult than nitrogen. Thus, according to the structure of the JP 2000-188399 A, reduction of the concentration in the surface layer of the n−type source region can be prevented so that a rise in contact resistance with respect to the source electrode is prevented.
Although the JP 2000-188399 A has disclosed a technology of preventing external diffusion of impurities in the surface layer (i.e., a region in which the concentration of the impurity is relatively high) of the n−type source region, behavior of the impurity in the deep layer (i.e., a region in which the concentration of the impurity is relatively low) of the n−type source region has not been considered. More specifically, as shown in FIG. 2 of the JP 2000-188399 A, channeling of the impurity has occurred in the deep layer of the n−type source region in the semiconductor device of the JP 2000-1888399 A. The channeling of the impurity in a relatively low concentration region may affect the characteristic of the semiconductor device.